The invention relates to a control device for the control of a shift clutch of a dobby such as is used for driving heald shafts of weaving machines.
Such dobbies comprise shift clutches with a control device that has been shown by document DE 697 01 619 T2, for example. The control device comprises a carrier that is driven so as to oscillate. A pivotally supported shift finger is provided on the carrier. In a first pivot position, this finger actuates one rocker arm, while a second rocker arm remains inactive. In its second pivot position, the selecting finger actuates a second rocker arm, while the first rocker arm remains inactive. The rocker arms are used to control a shift clutch in order to define whether or not an eccentric driving a specific heald shaft is to carry out (half) a rotation.
An electromagnet is provided for moving the shift finger that comprises an armature that is hinged to the selecting finger. The free end of the armature abuts against the electromagnet and delimits, therewith, a triangular air gap. The actuation of the selecting finger occurs against the force of a compression spring, said compression spring pushing the selecting finger away from the electromagnet into one of the two shift positions. If the electromagnet attracts the armature against the force of this compression spring, the selecting lever pivots into its other possible pivot position.
This design requires relatively few moved parts and a relatively high magnetic field strength.